Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H,W=map(int,input().split())
M=[input() for _ in range(H)]
dist=0
visited=[[False]*W for _ in range(H)]
q=deque([(0,0,0)])
visited[0][0]=True
while q:
    x,y,dist=q.popleft()
    for i in range(4):
        nx,ny=x+[-1,0,1,0][i],y+[0,-1,0,1][i]
        if 0<=nx and nx<W and 0<=ny and ny<H and M[ny][nx]=='.' and not visited[ny][nx]:
            q.append((nx,ny,dist+1))
            visited[ny][nx]=True
    if x==W-1 and y==H-1:
        c=0
        for m in M:
            c+=m.count('.')
        print(c-dist-1)
        exit()
print(-1)